1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to an ultrasonic medical device for destroying tissue in a controlled fashion within a human body.
2. Description of Related Art
Medical instruments utilizing ultrasonic energy to destroy tissue in a human body are known in the art. One drawback of existing ultrasonic medical instruments which remove tissue is that typically doctors have considered them to be slow in comparison to methods such as surgical excision. Part of the reason for this perceived slowness is explained by the fact that most existing ultrasonic devices rely on a longitudinal vibration of the tip of the probe. In other words, the tip of the probe is vibrated in a direction in line with the longitudinal axis of the probe. This produces a tissue destroying affect only at the tip of the probe.
One solution that has been proposed is to vibrate the tip of the probe in a transverse direction—i.e. perpendicular to the longitudinal axis of the probe—in addition to vibrating the tip in the longitudinal direction. For example, U.S. Pat. No. 4,961,424 to Kubota et al. discloses an ultrasonic treatment device to destroy and emulsify concretions or tissue in a human body. The Kubota et al. device produces both a longitudinal and transverse motion at the tip of the probe. The Kubota et al. patent, however, still relies solely on the tip of the probe to act as a working surface. Therefore, it improves the efficiency of the tip, but still relies on the tip of the probe to perform all cutting actions.
Although Kubota et al. describe providing a transverse motion at the tip of the probe, a transverse motion along the length of the probe has generally been discouraged. For example, U.S. Pat. No. 4,474,180 to Angulo discloses an ultrasonic kidney stone disintegration instrument with a damping material applied to the wire probe to inhibit lateral vibrations of the wire in the region of the connection to the ultrasonic transducer.
Another proposed method of improving the speed of ultrasonic tissue remove is oscillating the tip of the probe in addition to longitudinally vibrating the tip of the probe. For example, U.S. Pat. No. 4,504,264 to Kelman discloses an ultrasonic treatment device which improves the speed of ultrasonic tissue removal. In the Kelman device, the tip of the probe is vibrated longitudinally and also oscillated, so that the cutting efficiency of the probe tip is improved. Again, however, only the tip of the probe performs a cutting action.